title: An improved postconditioning algorithm: gradually increased reperfusion provides improved cardioprotection in rats.
abstract: The aim of the present study was to investigate whether a gradually increasing reperfusion algorithm, in which the brief reperfusion was lengthened as the duration of each reperfusion/reocclusion cycle remained fixed, enhances cardioprotection. Rats were randomized into 5 groups: the sham, reperfusion injury (R/I), gradually decreased reperfusion (GDR; 30/10‑25/15‑15/25‑10/30 sec of reperfusion/reocclusion), equal reperfusion (ER; 4 20/20‑sec reperfusion/reocclusion cycles) and gradually increased reperfusion (GIR; 10/30‑15/25‑25/15‑30/10 sec of reperfusion/reocclusion). The rats were sacrificed to measure serum markers, apoptotic indices and infarct size. Western blot analyses were used to analyze the expression of molecules involved in important signaling pathways. All the three postconditioning patterns were found to provide cardioprotection (P<0.05 compared with the R/I group). GIR provided optimum cardioprotection, followed by ER and then GDR. Apoptotic index and serum marker levels were significantly reduced in the GIR compared with the ER group (P<0.05). The enhanced cardioprotection provided by GIR was accompanied by significantly increased levels of extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation and Bcl‑2, as well as lower levels of p38/c‑Jun N‑terminal kinase (JNK) phosphorylation, tumor necrosis factor α (TNFα), caspase‑8, Bax, caspase‑9 and cytochrome c (Cyt‑c) in the cytoplasm of rats (P<0.05, all compared with ER). The infarct size in the rats of the GIR group was also smaller compared with that in the rats of the ER group, but this difference was not significant (16.30±5.22 vs. 20.57±6.32%, P>0.05). All the variables measured in the present study were significantly improved in the GIR group compared with the GDR group (P<0.05). In conclusion, the association between brief reperfusion and reocclusion is an important factor in postconditioning algorithms. Additionally, GIR results in improved cardioprotection compared with that achieved by the remaining algorithms examined.
authors.affiliation: Department of Cardiology, General Hospital of Jinan Military Command, Jinan, Shandong 250031, P.R. China.
authors.forename: Guoming
authors.initials: G
authors.lastname: Zhang
authors.forename: Yuanyuan
authors.initials: Y
authors.lastname: Sun
authors.forename: Yu
authors.initials: Y
authors.lastname: Wang
authors.forename: Jing
authors.initials: J
authors.lastname: Bai
authors.forename: Tiande
authors.initials: T
authors.lastname: Li
authors.forename: Xiaoyan
authors.initials: X
authors.lastname: Li
authors.forename: Shaoping
authors.initials: S
authors.lastname: Su
authors.forename: Xiuhua
authors.initials: X
authors.lastname: Liu
mesh_terms: D000465:Algorithms; D000818:Animals; D017209:Apoptosis; D015415:Biomarkers / Q000097:blood; D053181:Caspase 8 / Q000378:metabolism; D053453:Caspase 9 / Q000378:metabolism; D004195:Disease Models, Animal; D006439:Hemodynamics; D057775:Ischemic Postconditioning / Q000379:methods*; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D008297:Male; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases; D015428:Myocardial Reperfusion Injury / Q000378:metabolism / Q000503:physiopathology / Q000628:therapy*; D009206:Myocardium / Q000378:metabolism / Q000473:pathology; D032383:Myocytes, Cardiac / Q000378:metabolism / Q000473:pathology; D051381:Rats; D013997:Time Factors; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D051028:bcl-2-Associated X Protein / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D015415:Biomarkers; D014409:Tumor Necrosis Factor-alpha; D051028:bcl-2-Associated X Protein; D048031:JNK Mitogen-Activated Protein Kinases; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D053181:Caspase 8; D053453:Caspase 9